Relative density of urine: Difference between revisions
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By ''relative density of urine'' we mean the ratio of the density of urine to the density of water. The density of water is practically equal to 1 kg/l, so the difference between the density of water (in kg/l) and the relative density of urine is negligible. | |||
In the SI system, density has the dimension kg·m<sup>-3</sup>. The density of the sample in relation to the density of water is a relative quantity and is therefore given by a dimensionless number. | |||
===== Determination of density of urine ===== | |||
The density of urine is estimated indirectly by the concentration of cations using diagnostic strips. The indicator zone of the strip contains a suitable polyelectrolyte as an ion exchanger and the acid-base indicator bromothymol blue. The principle of diagnostic strips is based on the exchange of cations from urine, especially Na<sup>+</sup>, K<sup>+</sup>, NH<sub>4</sub><sup>+</sup>, for the H<sup>+</sup> ions of the polyelectrolyte in the indication zone. The released H<sup>+</sup> acidifies the weakly buffered acid-base indicator, which is in alkaline form. Acidification is accompanied by a change in color to bromothymol blue. The disadvantage is that examination with diagnostic strips does not take into account substances of a non-electrolyte nature such as [[glucose]], proteins, [[urea]], [[creatinine]] and some others. | |||
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== Links == | == Links == | ||
=== Related Articles === | |||
* [[Renal function test]] | |||
* [[Urine test]] | |||
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[[Category:Biochemistry]] | |||
[[Category:Clinical Biochemistry]] | |||
[[Category:Chemistry]] | |||
Latest revision as of 10:40, 15 February 2023
By relative density of urine we mean the ratio of the density of urine to the density of water. The density of water is practically equal to 1 kg/l, so the difference between the density of water (in kg/l) and the relative density of urine is negligible. In the SI system, density has the dimension kg·m-3. The density of the sample in relation to the density of water is a relative quantity and is therefore given by a dimensionless number.
Determination of density of urine[edit | edit source]
The density of urine is estimated indirectly by the concentration of cations using diagnostic strips. The indicator zone of the strip contains a suitable polyelectrolyte as an ion exchanger and the acid-base indicator bromothymol blue. The principle of diagnostic strips is based on the exchange of cations from urine, especially Na+, K+, NH4+, for the H+ ions of the polyelectrolyte in the indication zone. The released H+ acidifies the weakly buffered acid-base indicator, which is in alkaline form. Acidification is accompanied by a change in color to bromothymol blue. The disadvantage is that examination with diagnostic strips does not take into account substances of a non-electrolyte nature such as glucose, proteins, urea, creatinine and some others.
